Reprographic apparatus



Oct. 14, 1969 F, w, w s ET AL 3,471,882

REPROGRAPHIC APPARATUS med June 14. 1967 s Sheets-Sheet 1 l I -l 1 TUE L. F. w. LAWES ET AL REPROGRAPHIC APPARATUS 6 Sheets-Sheet 2 Filed June 14, 1967 Oct. 14, 1969 w, was ET AL 3,471,882

REPROGRAPHIC APPARATUS Filed June 14, 1967 6 Sheets-Sheet 5 FIG. 2

L. F. w. LAWES T AL 3,471,882

REPROGRAPHIC APPARATUS 6 Sheets-Sheet 4 Filed June 14. 1967 Oct. '14, 1969 w, wEs ETAL 3,471,882

REPROGRAPHIC APPARATUS 6 Sheets-Sheet 2 Filed June 14. 1967 Ot. 14, 1969 L. F. w. LAWES ETAL REPROGRAPHIC APPARATUS 6 Sheets-Sheet 6 Filed June 14, 1967 United States Patent 3,471,882 REPROGRAPHIC APPARATUS Louis F. W. Lawes, Walton-on-Thames, Nicholas Gilbert Shreeve, Weybridge, and Nandor Mihalik, Walton-on- Thames, England, assignors to Arlside Limited, Maidenhead, England, a British company Filed June 14, 1967, Ser. No. 645,975 Claims priority, application Great Britain, June 16, 1966, 26,904/ 66 Int. Cl. B41f 35/00 US. Cl. 151 11 Claims ABSTRACT OF THE DISCLOSURE Manual control means of reprographic apparatus, said means operating a main on-olt switch and also rendering operative and inoperative a sensitive-drum cleaning device and warning means for indicating when a web of fabric thereof requires replacement. Combined with drive for the cleaning device is timer means for maintaining it operative for a predetermined period, once initiated.

heater unit and other parts of a machine in which the heat- 7 er unit is incorporated.

The present invention relates, in general terms, to the structure and arrangement of such other parts and their relationship to one another and to the heater unit and the transport means for the original document.

According to the invention there is provided reprographic apparatus including an electrostatographic drum, main drive means connected to rotate said drum, a main switch for controlling said main drive means, and a cleaning device for said drum, said cleaning device comprising two spools, a web of cleaning fabric wound on and extending between the said spools, and a roller movable to a forward position in which it presses said web against said drum and resiliently urged to a backward position in which it releases said web from said drum surface, wherein there is provided manually operable means for moving said roller into said forward position thereof and wherein said manually operable means is arranged also to actuate said main switch and thereby initiate said main drive means.

The invention is described below with reference to the accompanying drawings, in which:

FIGURE 1 is a side view of a reprographic machine, showing the relationship to one another of the' heater unit and other parts described in the related application and other parts of the machine not described or shown in detail in the related application,

FIGURE 1A shows part of FIGURE 1 on a larger scale and in greater detail,

FIGURES 2 and 2A illustrate shown in FIGURE 1,

FIGURE 3 is a view of the machine from the side op posite to that shown in FIGURE 1,

FIGURE 3A shows part of FIGURE 3 on a larger scale and in greater detail,

FIGURE 4 is a fragmentary sectional view taken on the line IV-IV of FIGURE 1A, and

parts of a cleaning unit 3,471,882 Patented Oct. 14, 1969 ice FIGURE 4A is a fragmentary view of a door shown in FIGURE 4.

Referring to FIGURE 1, the illustrated machine comprises a heater unit 35 with an associated branch 57b of a duct 57 for air from a fan 27, a branch 57a of this duct leading to the vicinity of a lamp L for illuminating an original document fed into the machine over a feed table 13 and through an aperture (not visible in FIGURE 1) in a front wall 11 of the machine. Apart from a minor re-arrangement of a valve 58 in the branch 57b and of a solenoid 52 which controls it, these parts, and transport means for the original document to be copied (including rollers 15, 16, 17, 18, 19 and 20) are as described in the related application, as also is the control circuitry of the machine, and it will be unnecessary in this specification to repeat the detailed description which appears in the related application, in which the same reference numerals are used to indicate parts referred to both in the related application and in this present specification.

As an original to be copied is fed into the machine from the feed table 13 it is illuminated by the lamp L and is scanned, as it is moved by the transport means, by a stationary optical system 70 which is shown in outline in FIGURE 1 and which projects an image of the document on to a drum 71 of the machine which rotates clockwise as viewed in FIGURE 1. In known manner, the rotation of the drum 71 and the movement of the original to be copied are effected by a main drive of the machine and are so related that as the original document is scanned progressively there is no relative movement between the image and the drum surface on which it is projected.

The drum 71 is provided with a light-sensitive electrostatographic surface, which is charged electrostatically by means of a first corona discharge device 29 (above and to the left of the drum 71) before having the optical image projected on to it, and projection of the image on to it is effective to allow those parts of the drum surface on to which bright parts of the image are projected to discharge so as to form on the drum surface an electrostatic latent image of the original document. As the drum rotates, the latent image is developed by cascade develop ment by means of a developer unit 72, this developer unit being, suitably, as described in co-pending application Ser. No. 554,591, filed on June 1, 1965 (Patent No. 3,367,- 307, issued Feb. 6, 1968), and, more particularly, as shown in detail in FIGURE 4 of the specification thereof. The developer unit comprises, as described in that patent, a toner replenisher unit (indicated in the present application by reference 73) and a shutter controlled by a solenoid (indicated in the present application and in the related application by reference 51).

Continued rotation of the drum 71 brings the developed image on its surface to an image transfer station where, with the aid of a second corona discharge device 29, the developed image is transferred from the drum surface to a sheet of copy paper fed, at the appropriate time to bring it in register with the image on the drum, from a copy paper stack by means of a copy paper feed mechanism 74 and copy paper transport means 75. The copy paper, with the developed image transferred on to it, is stripped from the drum and fed along a guide or chute 32 to the nips between a driven roller 33 and a pair of rollers 34, which feed it into the heater unit 35 as described in the related application.

The drum surface, after the developed image has been transferred therefrom, passes to a cleaning station before returning once more to the first corona discharge device to be recharged.

At the cleaning station, the drum surface is subjected to the action of a cleaning unit indicated generally as 76. As shown in FIGURES 1 and 1A of the present application, the cleaning unit 76 comprises two spools 77 and 78, mounted on spindles 79 and 80 and freely rotatable relative thereto, with a web of cleaning fabric 81 rolled initially on the spool 77 and gradually taken up on the s ool 78. A pressure roller 82 of the cleaning unit is secured on a spindle 83 for rotation therewith, the spindle 83 being supported in mountings 84 which are displaceable to move the roller 82 into the illustrated position, in which it nips the fabric 81 against the surface of the drum 71, or into a retracted position towards which it is urged by springs 85 and in which there is a clearance between the roller 82 and the drum 71 so that the fabric 81 is released. As shown in FIGURE 2, the spindle 79 is fixed, being secured to a side wall 86 which, in FIGURE 1, is behind the spools 77 and 7 8. The spindles 80 and 83, on the other hand, are positively driven spindles which project through apertures in the side Wall 86. On the spindle 79 is mounted a friction clutch comprising (see also FIG- URE 2A) two semicircular members 87 and 88 which together frictionally embrace the spindle 79, with a small gap between them, and are urged together by a circular coil spring 89 which embraces them and is located in a groove formed round their peripheries. Each member 87 and 88 has two apertures 90, and one of these four apertures is engaged by a spigot 91 projecting from the spool 77 which is thus yieldingly retained against rotation relative to the stationary spindle 79. The spool 78 is provided with a similar spigot 92 engaging a similar friction clutch 93 which, accordingly, yieldingly urges the spool 78 to rotate with the driven spindle 80.

Whenever the main drive of the machine is applied to the spindle 83 (which, as described below, only occurs while the roller 82 is in its illustrated position) the roller 82 rotates slowly, carrying with it the part of the fabric 81 which is nipped between it and the drum 71, so that the part of the fabric which is bearing against the drum surface to clean it is continually being changed; as this takes place, the spool 77 is slowly rotated against the action of the clutch between it and the spindle 79, and the fabric advanced by the roller 82 is taken up by rotation of the spool 78, urged by the clutch 93 to rotate with the spindle 80. When all the fabric 81 has been wound off the spool 77, the used fabric and the two spools are removed and replaced by new spools provided with a fresh length of fabric. To facilitate this removal and replacement, the ends of the spindles 79 and 80 which are remote from the side wall 86 are journalled (as shown in FIG- URE 1) in brackets 94 and 95 which are hingedly mounted at 96 and 97 so that they can be swung away to leave the ends of the spindles clear for withdrawal of the spools 77 and 78 thereover-the fabric 81 being free to slide in the clearance between the drum 71 and the roller 82 in its retracted position.

The main drive of the machine is provided, as described in the related application, by an electric motor 26 which, through a reduction gear, drives a chain sprocket 100 shown in FIGURES 3 and 3A. The sprocket 100 drives an endless chain 101 which transmits the drive to the various parts of the machine. Following the chain 101 in the direction in which it is driven (generally clockwise as viewed in FIGURE 3) it passes under a spring-urged tensioning sprocket 102, round a free-running sprocket 103, over a drive sprocket for the roller (this being one of many reference numerals used herein to refer to or indicate parts described in detail under the same reference numeral in the related application), round a sprocket 104 geared to the roller 49, under a free-running sprocket 105, under a drive sprocket for the roller 33, round a sprocket 106 adjustably mounted for tension adjustment of the chain 101, round a drive sprocket 107 for the copy paper feed mechanism, under a drive sprocket for one of a pair of rollers 108 and 109 of the copy paper transport means, round a drive sprocket 110 geared by bevel gears to a rotary elevator of the developer unit 72, round a drive sprocket 111 for the toner replenisher unit 73, round a sprocket 112 geared to the drum 71, round a sprocket 113 (further referred to below), over a sprocket 114 secured on the spindle of the cleaning unit, round a drive sprocket for the roller 16, and back to the sprocket 100.

Energisation of the motor 26 immediately applies drive to the drum 71, the original document transport means (rollers 15 and 16), the copy paper transport means (rollers 108 and 109, rollers 33 and 34 and rollers 49 and 50), the developer unit rotary elevator (sprocket and to the spindle 80 of the drum cleaning unit 76; and makes drive available at the sprockets 107 (for the copy paper feed mechanism), 111 (for the toner replenisher unit), and 113.

The sprocket 107 is connected through a magnetic clutch (not shown) to the copy paper feed mechanism which is briefly actuated at the appropriate time to advance one sheet of copy paper from a stack into engagement with the copy paper transport means, specifically the rotating rollers 108 and 109 which take up the copy sheet between them. Actuation of the copy paper feed mechanism is effected by energising the magnetic clutch and this in turn is achieved by having the magnetic clutch connected to the leads 31 shown in FIGURE 3 of the related application.

Similarly, the sprocket 111 is connected to the toner replenisher unit 73 through a second magnetic clutch (not shown) which is connected to the leads 55 in FIGURE 3 of the related application so as to be energised at the appropriate time.

The sprocket 113 provides the drive for the spindle 83 and roller 82 of the cleaning unit 76 and for a mechanical timer equivalent to the timer 56 shown in FIG- URE 3 of the related application and controlling the switch MS6 of that figure. As shown in FIGURE 3 of the accompanying drawings, the sprocket 113 is connected through bevelled gears 115 to a shaft 116, which in turn is connected through a magnetic clutch 117 to a shaft 118 on which is mounted a worm year 119. The Worm 119 meshes with a worm wheel 120 mounted for rotation with a cam disc 121 which co-operates with the switch MS6 described in the related application. The magnetic clutch 117 is connected to the leads 55 of the related application, and it will be seen that as soon as the switch MSS thereof closes, the clutch 117 becomes energised and transmits the drive from the sprocket 113 to the cam disc 121 which begins to rotate and thus first closes the switch MS6 and then holds it closed (so that the clutch 117 remains energised) until the cam disc has performed one third of a revolution whereupon the switch MS6 opens and the clutch 117 becomes de-energised. Thus the cam disc and its drive constitute or are equivalent to the timer 55 of the related application. The worm 119 also meshes with a worm wheel 122 mounted on the cleaner unit spindle 83 for rotation therewith. It will be appreciated that movement of the roller 82 between its position illustrated in FIGURE 3 and its retracted position is not prevented by the engagement of the worm wheel 122 with the worm 119, but merely involves some rotation of the roller 82 as the worm wheel 122 rolls along the worm 119, and that with the roller 82 in a fixed position (in particular, fixed in its illustrated position) drive is transmitted from the sprocket 113 to the roller 82 whenever the clutch 117 is energised.

Movement of the roller 82 between its retracted and illustrated positions is effected manually at the same time as the main switch 25 of the machine is operated. The rear ends of the displaceable mountings 84 are formed as cam followers for co-operation with cams 125 mounted on a shaft 126 for rotational movement therewith. As shown in FIGURE 1, the cams 125 (of which one is shown) are shown in their position corresponding to the retracted position of the roller 82 and it will be appreciated that in practice, with the cams 125 in the position illustrated, the springs 85 would retract the roller 82 by moving the mountings 84 to engage the cams with their camfollower ends. Rotation of the shaft 126' clockwise (as shown in FIGURE 1) from its illustrated position as limited by a stop 127 to a position in which the stop 127 is engaged by a projection 125' on the cam 125, moves the mountings 84 to their illustrated position, the last part of this movement being along a dwell portion of the cam. The shaft 126 is provided with a knob 126' (see FIGURE 4) for effecting this movement manually. The shaft 126 also carries a second cam 128 which c0- operates with the main switch 25 of the machine, this switch being a microswitch as illustrated. The cam 128 has a rising portion 128 and the switch 25 is arranged to close under the action of this portion 128, at a time when the roller 82 has already reached its illustrated position and the rear ends of the mountings 84 are already on the dwell portions of the cams 125. Thus the machine does not become switched on until the fabric 81 is firmly and positively in cleaning relationship With the drum 71. The switch 25 is arranged to stay closed, when the shaft 126 is turned anticlockwise (in FIGURES 1 and 1A), until the cams 125 and 128 are almost in their illustrated position, so that as the machine is switched off the main drive continues (and the drum 71 continues to rotate) until after the roller 82 has been allowed to retract under the urging of the springs 85 and thus to release the fabric 81 from the drum 71. It is thus ensured that the fabric 81 is never allowed to remain pressed against the drum while the drum is stationary after the apparatus has been switched off-a condition which would be liable to impair the drum surface.

The cam 128 is formed with a projecting arm 129 which, as it moves to its illustrated position, bears on an arm 130, mounted on a shaft 131, to turn the shaft 131 anticlockwise. The shaft 131 carries a feeler 132, and on the machine being switched on and the arm 130 being released by the arm 129, the shaft 131 turns clockwise until the feeler 132 comes into engagement with the fabric 81 which still remains rolled on the spool 77. It will be understood that the extent to which the shaft 131 rotates increases as the spool 77 approaches its empty condition in which replacement of the spools 77 and 78 and the fabric 81 is required. As shown in FIGURE 3A, the shaft 131 has mounted thereon, for rotation therewith, a lever 134 which is biased by a spring 135 to urge the feeler 132 anticlockwise as viewed in FIGURE 3A (clockwise as viewed in FIGURES 1 and 1A) into engagement with the fabric 81 on the spool 77. The lever 134 is formed with an arcuate slot 136 into which projects a pin 137 projecting from a trip disc 138 mounted to be freely rotatable on a pivot 139. The trip disc 138 in its illustrated position holds a striker 140, freely rotatable about a pivot 141, in its illustrated position and out of engagement with a warning bell 142. So long as a supply of fabric 81 remains on the spool 77, the slot 136 is long enough to accommodate movements of the shaft 131 as the machine is switched on and 011, without disturbing the pin 137 and trip disc 138. When the spool 77 is empty, however, or almost empty, the anticlockwise movement (in FIGURE 3A) of the shaft 131 as the machine is switched on is suificient to bring the clockwise end of the slot 136 into engagement with the pin 137 and thus to rotate the trip disc 138 suliiciently clockwise to release the striker 140 so that its head 143 can strike the warning bell 142. The striker 140 is formed with a tail 144 which, in the released position of the striker, rides over teeth of a wheel 145 mounted with the sprocket 100 for rotation therewith; and the striker is thereby caused to reciprocate, under the action of its own weight and the rotating toothed wheel 145, and to strike the bell 142 repeatedly as a warning that the cleaning fabric 81 is exhausted and requires replacement. When the machine is switched off, the clockwise movement of the lever 134 causes the anticlockwise end of the slot 136 to engage the pin 137 and reset the trip disc 138 and the striker 140 in their illustrated positions; but the bell will, of course, begin to ring again when the machine is next switched on, unless a full spool 77 has been fitted meanwhile.

It may be mentioned at this point that, although the fabric 81 may very suitably be a fabric woven from spun rayon, it may also be an unwoven fabric of soft paper tissue similar to that which is widely used nowadays in the form of paper tissue handkerchiefs, inter alia. Furthermore the fabric, whether of woven spun rayon or of paper tissue or of some other material may advantageously be impregnated with a liquid, suitably an oil, to a sufficient extent to provide the drum surface with a thin liquid film in addition to cleaning it.

Reference has been made above to the copy paper feed mechanism 74, which will now be briefly described with reference to FIGURE 1. It comprises a pair of arms joined by a cross bar 151 and freely pivotable together, about a shaft 152. Between the free ends of the arms 150 is mounted a freely rotatable shaft 153 having, near its outer ends, two rubber-covered rollers 154 which are mounted on the roller 153 by free-wheel devices which allow them to rotate anticlockwise relative to it. At its centre, the shaft 153 has mounted on it a sprocket for a chain drive which also passes round a sprocket secured on the shaft 152 for rotation therewith, and the shaft 152 is coupled to the sprocket 107 through the magnetic clutch which is not illustrated but which has already been mentioned as associated with the sprocket 107. When this clutch is energised, the shafts 152 and 153 are accordingly rotated anticlockwise (in FIGURE 1), as also are the rollers 154 which rest on the top sheet of the stack of copy paper and which, on being rotated, advance this top sheet so that its leading edge is guided by a guide 155 of the copy paper transport means and becomes engaged between, and taken up by, the rollers 108 and 109 thereof. The copy paper feed mechanism is only operative for a short while, but when its drive is discontinued, on deenergisation of the associated magnetic clutch, the rollers 154 are free to overun the shaft 153 as the top copy sheet continues to be drawn off the stack, by the rollers 108 and 109. The stack of copy paper is accommodated in a removable tray 156 of which only one end is shown, in a partly withdrawn position, and this tray is provided with cam blocks 157 which cooperate with lever arms 158 mounted on the machine side walls and spring-urged to rotate clockwise to their illustrated position in which they bear on outboard extensions 159 of the bar 151 and raise the copy paper feed mechanism to its illustrated position which is, in fact, its inoperative position. In this inoperative position the rollers 154 are raised clear of the stack of copy paper in the tray, which may therefore be pushed fully home, i.e., to the right, without interference from the roller 154. Only as the tray is pushed fully home do the cam blocks 157 engage the levers 158 and rotate them anticlockwise, thereby releasing the copy pap-er feed mechanism so that the rollers 154 come to rest on the top sheet of copy paper.

Returning now to the shaft 126 which carries the knob 126 by which the machine is switched on, it will be seen that this shaft is provided with a radially projecting peg 168 (which would normally be covered by the knob). This peg 160 is intended for co-operation with a door 168 (shown in FIGURES 4 and 4A) of an outer cover 169 of the machine, this section being mounted on hinges 170 so as to give access to the cleaning unit for swinging the arms 94 and 95 outwardly and replacing the spools 77 and 78 and fabric 81. The hinged door 168 has a circular aperture 171 through which the end of the shaft 126 protrudes (when the door is in its normal position) to receive the knob, and the circular aperture is extended in a radial ly-extending slot 172 so that the door can be swung open only when the peg 160 is aligned with the slot 172, i.e., is in its illustrated position in which the machine is switched off, as shown in FIGURE 4A. To prevent the machine from being inadvertently switched on by twisting of the shaft 126 while the cover section is hinged down,

the arm 129 is formed with an aperture 161 into which a peg 162, mounted on a leaf spring 162, is urged by the spring. With the aperture 161 engaged by the peg 162', rotation of the shaft 126 is prevented. The door 168 carries an inward projection 168' which, when the door 168 is in place, bears against the spring 162 as shown in FIG- URE 4 and prevents the peg 162 carried thereby from entering the aperture 161.

Although the fan 27 is described in the related application as being separately powered, and not as being driven by the main drive motor 26, it may in fact conveniently be so driven. In an advantageous arrangement, the motor 26 drives the sprocket 100 through a speed-reduction gear and is also mechanically coupled to the fan 27, which then has no separate driving motor, through a speed-increasing gear.

As may be seen in FIGURE 3, the side wall 86 of the machine is formed with an aperture 165 for the escape of ventilating air supplied to the heater unit 35 by the fan 27 through the duct 57b whose lower end opens inwardly through the opposite side wall; and this aperture 165 also gives access to heater elements 41 of the heater unit so that these may be removed and replaced, when desired, without disassembling the machine other than removing an outer cover with which it is provided (and of which the hinged cover section referred to above is a part). In the event of a sheet of copy paper becoming fouled in the heater unit, the lower part thereof (including a support plate 38 over which the paper normally slides and strengthening bars 42 and insulation 44 therefor as shown in the related application) can also be removed. For this purpose, the roller 50 can be pulled obliquely downwardly (after withdrawal from the machine of the copy paper tray which normally extends below the heater unit) so the lower part of the heater unit can be removed by pulling it forwardly between the roller 49 and the roller 50 when separated therefrom.

The rollers and 16, and a conveyor band 14 passing round them, are also assembled as a removable unit provided with slides 166 engaging in slide ways 167 in the side walls of the machine; and this unit can also be removed by pulling it forwardly after disengaging the drive chain 101 from the sprockets of the rollers 15 and 16.

What we claim is:

1. Reprographic apparatus including an electrostatographic drum, main drive means connected to rotate said drum, a main switch for controlling said main drive means, and a cleaning device for said drum, said cleaning device comprising two spools, a web of cleaning fabric wound on and extending between the said spools, and a roller movable to a forward position in which it presses said web against said drum and resiliently urged to a backward position in which it releases said web from said drum surface, wherein there is provided manually operable means for moving said roller into said forward position thereof and wherein said manually operable means is arranged also to actuate said main switch and thereby initiate said main drive means.

2. Reprographic apparatus as claimed in claim 1, and including slidable mountings having said roller mounted at forward ends thereof and having rear ends formed as first cam followers, said manually operable means comprising a rotatable shaft having mounted thereon respective cams engaged by said first cam followers.

3. Reprographic apparatus as claimed in claim 2, wherein said shaft also has mounted thereon a further cam and said main switch includes a second cam follower engaged with said further cam, said first cams having dwell portions which permit further rotation of said shaft with said roller in the forward position thereof and said main switch being arranged to be actuated by said further cam during said further rotation of said shaft.

4. Reprographic apparatus as claimed in claim 3, wherein said roller is provided with a worm wheel and there is provided a worm which engages said worm wheel and on which said worm wheel rolls during movement of said roller between said forward and backward positions thereof, there being further provided a magnetic clutch having an input side connected to said main drive means and an output side connected to said worm, whereby said roller is driven by said main drive means when said magnetic clutch is energised, and wherein there is further provided a second worm wheel engaging said worm, a cam disc secured for rotation with said second worm wheel and a circuit-holding switch having an actuating member engaged with said cam disc said circuitholding switch being connected in series in an energising circuit for said magnetic clutch, whereby when said magnetic clutch is once energised said cam disc actuates said circuit-holding switch to maintain said magnetic clutch energised until said cam disc and said roller have rotated predetermined amounts determined by the profile of said cam disc.

5. Reprographic apparatus as claimed in claim 2, wherein said main drive means is connected through a slipping clutch to drive one of said spools to wind said fabric web thereon and the other of said spools is yieldingly held against rotation, and wherein there is provided a feeler resiliently urged towards contact with said fabric web wound on said other spool, and an arm, secured on said shaft and holding said feeler out of said contact when the position of said shaft is such that said first cams and said further cam allow said roller and said main switch to assume respectively its backward position and its unactuated condition.

6. Reprographic apparatus as claimed in claim 5 and provided with an alarm bell, a pivotally mounted striker having a first end engageable with said bell and a second end, a toothed wheel driven by said main drive means and engageable with said second end to pivot said striker and move the first end thereof repeatedly into and out of striking engagement with said bell, trip means movable between first and second positions in which it respectively frees said striker for engagement with said bell and said toothed wheel, and a lost-motion linkage between said feeler and said trip means and arranged to move said trip means into said second position thereof when said feeler is moved out of contact with the fabric web on said other spool and to move said trip means into said first position thereof when said feeler moves to a predetermined position in the direction in which it is resiliently urged.

7. Reprographic apparatus as claimed in claim 2 and provided with two mutually parallel spindles having the said two spools mounted thereon, each of said spindles being permanently supported at one end and there being provided for supporting the other end of each spindle a support arm which is disengageable from the respective spindle whereby the said two spools can be withdrawn from the said spindles over the said other ends thereof.

8. Reprographic apparatus as claimed in claim 7, and provided with a displaceable cover plate which normally covers said support arms and which is provided with an aperture through which said shaft then projects, said shaft having a radial projection outboard of said cover plate and said cover plate aperture having a peripheral recess whereby outward movement of said cover plate is unobstructed by said projection in only one rotational position of said shaft.

9. Reprographic apparatus as claimed in claim 8 and provided with detent means for engaging said shaft in said one rotational position thereof and preventing rotation thereof, and means on said cover plate engaging said detent means and preventing engagement thereof except when said cover plate is moved outwardly.

10. Reprographic apparatus as claimed in claim 1, wherein said roller is provided with a worm wheel and there is provided a worm which engages said worm wheel and on which said worm wheel rolls during movement of said roller between said forward and backward positions thereof, there being further provided a magnetic clutch having an input side connected to said main drive means and an output side connected to said worm, whereby said roller is driven by said main drive means when said magnetic clutch is energised.

11. Reprographic apparatus as claimed in claim 10, wherein there is further provided a second worm wheel engaging said worm, a cam disc secured for rotation with said second worm wheel and a circuit-holding switch having an actuating member engaged with said cam disc, said circuit holding switch being connected in series in an energising circuit for said magnetic clutch, whereby when said magnetic clutch is once energised said cam disc actuates said circuit-holding switch to maintain said magnetic clutch energised until said cam disc and said roller have rotated predetermined amounts determined by the profile of said cam disc.

References Cited UNITED STATES PATENTS 10 WALTER A. SCHEEL, Primary Examiner L. G. MACHLIN, Assistant Examiner U.S. Cl. X.R. 

